Polyhedral conversion
This MR implements the conversion of prism to polyhedron, by atomic extrusion operation.
TODO: Talk about how far this method should be used: Prisms can be on a base plate of any type, they are usually not triangulated. Since they are not triangulated the volume calculation will return wrong results one converted.
It should also be discussed if the atomic operations should be exposed by the API or just kept anonymously
Edited by Ludwig Jaeck